1. Field of the Invention
The present invention relates to amplifiers, particular amplifier integrated circuits having an on-chip inductor.
2. State of the Art
Different mobile communications systems are prevalent in different geographical regions. Example systems include those specified by the GSM and ANSI-136 standards, which are time division multiple access (TDMA) communication systems, the CDMA standard (IS-95) and combinations of the same (so-called multi-mode systems). Furthermore, the proliferation of competing standards is increasing with the adoption of different 2.5 and 3G mobile communications standards, such as EDGE, UMTS (WCDMA), CDMA2000, etc. Hence, although the vision of a xe2x80x9cworld phonexe2x80x9d has been repeatedly articulated, actually building such a phone economically has proved challenging.
For a multi-band phone, a multi-band amplifier is required, typically provided in the form of a semiconductor product. Dual-band, tri-band, and even quad-band phones have entered production or been the subject of discussion. Such amplifiers have typically required substantial duplication and exhibited very little sharing of components. Hence, if a single band amplifier required X mm2 of semiconductor area, a dual-band amplifier would typically require close to 2X, a tri-band amplifier close to 3X, etc. As the number of bands supported increases, the attractiveness of such a model greatly decreases.
An improvement is therefore sought to increase the density of integration of multi-band amplifiers.
An amplifier circuit formed on a single semiconductor substrate includes a first amplifier having at least one stage for amplifying signals within a first frequency band; a first amplifier having at least one stage for amplifying signals within a second frequency band; and a tapped coil having one end thereof coupled to a stage of the first amplifier and a tap thereof coupled to a stage of the second amplifier. The amplifier circuit may be an RF amplifier circuit, a first portion of the tapped coil serving as an RF choke for said stage of the first amplifier, and a second portion of the tapped coil serving as an RF choke for said stage of the second amplifier. Sharing the tapped coil between multiple band amplifiers increases integration density.